The invention relates to a door closer and to a method for the manufacture of a door closer.
Door closers are known which have closing springs as energy accumulators and a hydraulically damped closing movement, in which the closing spring cooperates with a hydraulic piston-and-cylinder unit. The piston-and-cylinder unit and the closing spring are disposed in a metal housing and cooperate through a rack and pinion or through a cam disk drive with a closer shaft journaled in the housing, which is connected directly or through a force-transmitting articulation to the door. When the door is opened manually the energy accumulator is charged and afterward discharged again in the automatic closing of the door. Upon each opening and closing movement of the door, the action of the piston causes hydraulic medium to be exchanged between the two piston working chambers through hydraulic passages disposed within the housing. A door closer of such construction is disclosed, for example, in EP 328 912 B1 or DE 38 353 A1.
Such door closers are known in practice in various versions. There are kinds which are mounted flat on the door or on the frame, and kinds which are integrated in the door frame. Scissor articulations or sliding arm articulations are used as the force-transmitting articulations. The housing of the door closer is made in practice of cast aluminum or from aluminum extrusions. The cost of manufacture is relatively high on account of the necessary machining. The hydraulic passages must be bored into the housing and the cylinder chamber must also be machine-finished in order to assure a precise seating of the piston.
DE 195 29 168 A1 describes a hydraulic door closer which consists of an elongated one-piece housing. The housing can be made of metal or also from polymer materials, and has a cylindrical longitudinal bore to accommodate the piston and a cross bore to accommodate the closing shaft. The exchange of the hydraulic medium takes place through a valve which is disposed in the housing cover and extends axially into the piston chamber and at the same time plunges into an axial bore in the piston. The housing itself does not have any hydraulic passages.
The invention is addressed to the problem of developing a housing for a door closer which will be easy to manufacture and machine, as well as developing a method for its manufacture.
The problem is solved according to the invention by the use of fiber-reinforced, preferably glass fiber- or carbon fiber-reinforced plastic offers special advantages in regard to strength and fashioning. Finish machining can be reduced or entirely eliminated. Also, advantageous friction properties are achieved by the use of a suitable combination of materials. Also, coatings and overlays of plastic on the housing interior wall, e.g., on the cylinder""s interior wall, or also on the outside wall of the piston can be provided advantageously, and plastic coating on metal walls or on sandwich materials is possible.
By the use of suitable combination of materials, e.g., valves and valve seats in the housing, the desired temperature-independence of the valve adjustment can be obtained by appropriate temperature compensation of the materials. A combination of different plastics as well as a combination of metal and plastic can be used.
Special advantages are obtained if the plastic material is dyed to the final color of the door closers, so as to eliminate the need to lacquer or otherwise finish-coat the closer to the final color or to simplify separate external coloring operations.
In the door closer housing, bore chambers, e.g., a passage in the housing, a mounting bore and/or space to accommodate an output member, a damping piston, a closing spring, a closing motor or a valve can be already formed in the door closer housing, at least section-wise, without machining, when the housing is formed, or at least it can be preformed without machining operations. Alternatively, or additionally, the formation of at least one bore chamber is performed during the assembly of several separately made housing parts, the bore chamber being created without machining in the contacting surfaces of the housing parts or at least being preformed without cutting operations.
Since such bored chambers are formed while the door closer housing is being made by an appropriate injection mold when the door closer housing is produced, the manufacturing cost is considerably reduced. As a rule, no further machining operations are necessary. The housing is at least partially, but more advantageously entirely manufactured from plastic. Manufacture is performed, for example, by the injection molding method. This method also makes it possible in a single manufacturing process to install, for example, a shaft bearing for the output shaft by the two-component method.
Furthermore, it is possible by using plastic to produce the door closer housing from a plurality of separate housing parts and simply glue or weld them together. The cylinder chamber can be closed after installation of the piston and closing spring by means of an end plug which is welded onto the cylinder chamber. It is therefore not necessary to form a screw thread in the cylinder chamber or on the plug.
Alternatively, the cylinder chamber can be closed by an end cap cupped around the cylinder chamber while hydraulic passages are formed with its marginal sections.
In the door closer housing, recesses can be created for separately made insert parts which are welded or cemented into the recesses. At the same time, passage sections of the damping device can be formed or preformed in the confronting faces of the door closer housing and of the insert. This method is especially suited for the formation of longitudinal passages which are brought out at the end of the housing for the insertion of the hydraulic valves. The radial passages connecting the longitudinal passages to the cylinder chamber are preferably already formed in the housing during production of the latter, without machining.
In another embodiment the door closer housing is made from two halves, in which the longitudinal halves of the cylinder chamber are formed. At the same time channels or channel sections of the door closer can be formed in confronting surfaces of the housing halves.
In another embodiment of the invention it is possible to make the piston and in some cases the output shaft wholly or partially of plastic, preferably however from a plastic-metal composite material. In that case the basic body of the piston is made from plastic, while recesses for sealing rings as well as passages for check valves can be already formed. Then a rack made of metal is placed or cemented into a corresponding recess in the piston.